Static Phase Converter

JTknives

JTknives

Joined
Jun 11, 2006
Messages
8,651
as many of you know i have a 5hp 3ph beast of a motor. im going to be building a static phase converter to use intell i get a VFD. i have been doing a ton of research and found this.

converter.gif


what it does is it sences the speed of the motor from the voltage created on the 3rd unused phase. it then disingages the starting circuit at full speed. if you are using the motor and you slow it down the starter cap ingages and brings up the speed. ideas?
 
i have read that the static phase converters dont work very well unless there ballanced. and thats the job of the caps.
 
a dimmer is not a variable resistor. A dimmer is a triac device that when energized above threshold switches on and stays switched on until current on it's switched leg is zero. It it adjusted by effectively using a potentiometer to limit voltage to its input leg (a bit more involved but . . . ) when it reaches threshold on its input leg it switches on until the sine wave through it's switched leg reaches zero potential and switches off effectively limiting how much of the sine wave the load sees. I do not think that a dimmer is what you want in your circuit. Beyond that, do you have 30 amps plus losses available to drive your motor where you plan to use it? My 5 horse (single phase 220) lathe has a minimum recommended 30 amp supply, and I imagine you are going to need at least that much current available plus your conversion losses.

-Page
 
I agree with what Page says. You also didn't take into account that you will lose several horsepower by using a static converter.They really don't work very well for this application ,if any.Save your money and get a VFD and your problem will be solved.Dave
 
You will want 30 amp service. A 20 amp breaker will be close enough to the full load amperage that you will have nuisance trips...
 
I built one once. You need a really big three phase motor, like twice as big as the one you are trying to run, a small single phase motor to start/spin it, and a bank of capacitors. That's all I remember. It was a long time ago. You might be better off just getting a single phase motor, or having three phase piped in.
 
Back when I did it, I was forced to because they didn't make a single phase motor with a slow enough RPM for what I needed, and I couldn't get three phase piped in for a reasonable price...

I have no idea what it's like today...
 
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